Complete Lecture - Govind Ballabh Pant Institute of Himalayan ...

The species of Rhododendron are shrubs or trees with leaves in terminalrosettes bearing flowers of a wide range of colours, shapes and sizes. They areproverbially slow –growing and range in size from 5cm in the alpine zone to giantsexceeding 25m in height. The craze for cultivation of rhododendrons, including azaleasof horticulture in the 19 th Century Western Europe is comparable to tulipomania. Over500 species have been cultivated in Great Britain alone. Concentrated efforts weremade to introduce and hybridize particularly the Asiatic species by the wealthy andprivileged (Mabberley, 1997). Over 1000 cultivars, mostly hybrids between Americanand Asiatic species are commercially available as potted plants and for planting asshrubs in gardens.R. arboreum was introduced from India to Britain in 1815 (Vishnu Swarup, 1997).The history of the visit of J.D. Hooker (1817-1911) to India has been colourfullyrecorded by many, notably Rix (1981). J.D. Hooker, who is immortalised as the authorof the Flora of British India (1872-1897), was persuaded by Dr. Falconer,Superintendent of the then Calcutta Botanic Garden, to travel to Sikkim – an unexplored paradise for botanists. Arriving at Calcutta in 1848, J.D. Hooker visitedDarjeeling and thence Sikkim. The book “Rhododendrons or Sikkim Himalaya”appeared between 1849 and 1851 with 30 folioplates drawn and lithographed by Fitch.Hooker introduced R. thomsonii, R. falconeri, R. cinnabarium and the subtropical R.dalhousiae, an epiphyte growing on the trunks of oaks and Magnolia cambelli to Britainwhere they became favorite garden plants (Rix, 1981). These species were followed byR. edgeworthii, R. grande, and R.griffithianum (Vishnu Swarup, 1997). The species fromthe Himalayas which were entirely different from those grown earlier in flower colourand form, foliage and stature, rapidly became popular in gardens. It was after Wilson,Forrest and Rock visited western China that the full impact of the wide spectrum of floralsplendour of the genus was realized.About 98% of the Indian species of Rhododendron are found in the Himalayanregion, out of which 72% occur in Sikkim. The genus forms a dominant component ofthe cool temperate and sub- alpine forests and alpine meadows of the Sikkim Himalaya.Therefore, Sikkim is the most appropriate location for conservation and propagationstudies of rhododendrons. Owing to several anthropogenic activities, the naturalpopulations of Himalayan rhododendrons are rapidly dwindling. The major threats aredeforestation, unsustainable extraction for fire wood and burning of twigs and leaves forincense by local people. These precious plants may be wiped out unless properconservation measures are not taken immediately. Rhododendrons support a widerange of birds and butterflies. Therefore, employment of this genus as a key stoneelement in these high altitudes would substantially contribute to conservation of habitatbiodiversity. Both conventional and biotechnological methods are urgently needed forconservation, propagation and restoration of rhododendron populations in the wild.These measures would require generation of baseline data on the present status ofdistribution and population sizes of the species, a thorough study of their reproductivebiology, development of methods for mass propagation using conventional and tissueculture techniques, hardening the plants raised and establishment of a gene pool bankas has been recently initiated at Pangthang. Till now there has been no substantial13